Mold and mildew can be a nuisance on any exterior building surface, regardless of the material. If the conditions are right, they will spawn on wood, plastic, concrete, metal and other surfaces. Mold formation is most prevalent in consistently wet, shaded areas. Spores from the natural environment are carried by the wind and commonly land on decks surfaces. It is important to note that the appearance of mold and mildew is a function of nature, not necessarily a deficiency with any of the material on which it grows.
Periodic washing with soap/detergent and water will help remove surface dirt. This will also help prevent the buildup of pollen, debris and spores that can cause and accelerate mold/mildew growth (it also helps to remove deck mold). Caution: A pressure washer should not be used to “blast” mold/mildew or soils from a deck surface. The abrasive nature of the water stream can potentially damage the material by driving the spores into the material, which may create a morechallenging problem to remediate. A pressure washer with a fan-tipped nozzle should be used only to lightly wet or rinse wood or composite deck surfaces.
There are many deck wash and exterior cleaning products available at retail. It is important to make sure you use a cleaner specifically intended for your application. After selecting a product, be certain to read, understand and follow all instructions supplied by the manufacturer. Some cleaning products and inhibitors may be more effective than others, depending on the environmental conditions your deck is subjected to. Additionally, it is always a good idea to test the cleaner in a small, inconspicuous area prior to applying it to the entire deck.
As with deck washes, there are several mold-inhibitor products available from paint stores, hardware stores, online outlets and home centers to help prevent long-term mold/mildew growth. For any product selected, be certain to read, understand and follow all instructions provided by the manufacturer. Depending upon the environmental factors affecting your composite lumber or treated wood deck, some preventive cleaning products may be more effective than others. It may be necessary to try more than one product. For ongoing preventive maintenance, follow the manufacturer’s recommendation.